Fig. 4.

Normal visual discrimination learning and memory independent of swimming dysfunction in R6/2 mice. Control (n = 17) and R6/2 (n = 14) mice were tested between 3 and 9 weeks of age. Control and R6/2 mice displayed a comparable degree of acquisition of a two-choice swim tank visual discrimination task at 3–4 weeks of age, and both groups maintained performance criterion until 8.5 weeks of age (A). On removal of the light stimulus at 9 weeks of age, performance declined to chance levels for both groups. R6/2 mice displayed swimming impairments from 5 weeks of age, which progressively worsened, as compared with controls (B). Motoric dysfunction failed to impair performance of R6/2 mice in the two-choice swim tank task.Vertical bars indicate means ± SEM of each measure across all trials at each age. Asterisks indicate significant differences between control and R6/2 mice (*p < 0.05; **p < 0.01).